Technically with the Apple, you will have iCloud if you have the internet operating. This IS a backup system. But as with any other system, you will need to configure iCloud to include your accounting data as an item you want backed up. The Mini is a great way to get started with Apple. Don't let it's size deceive you.

Edit: I do not have virus protection on any of my Macs and quite frankly, I'm unaware of any Mac users that do at this point.